From 2006-2012, hospitals didn’t lower use but often skipped first-line treatments.

On Wednesday, the United Nations will hold a historic meeting to take on the growing problem of antibiotic resistant microbes, which it called “one of the biggest threats to global health.” And according to new data from the Centers for Disease Control and Prevention, they have their work cut out for them. It turns out that not even hospitals in the US are taking the threat seriously enough.

Looking through hospitals’ prescription records from 2006 to 2012, the CDC found that the overall amounts of antibiotic prescriptions have held steady. That finding bucks warnings from the CDC and other public health agencies’ that doctors (as well as meat producers) are overusing and misusing the drugs and need to cut back. The CDC estimates that at least a third of antibiotic prescriptions in the US are unnecessary. Needlessly exposing microbes to antibiotics gives germs more opportunity to develop resistance to the otherwise life-saving drugs. Already, antibiotic-resistant infections strike 2 million people each year in the US alone, killing at least 23,000. Doctors and veterinarians need to cut back and use the drugs more wisely, the CDC has warned—apparently to no avail.

Looking through the prescription data, the CDC noted that although doctors seemed to be ignoring their warnings, they couldn’t ignore the problem of resistance. Though overall levels of antibiotics plateaued, doctors are increasingly skipping over antibiotics that are considered first-line defenses. Instead, they’re turning to second, third, and even some last-line drugs, which are more powerful but often come with more side effects. In the six-year study period, doctors upped their use of last-resort carbapenem antibiotics by 37 percent, according to the data published in JAMA Internal Medicine.

Experts in particular fear that misuse of these back-up and last resort drugs will spawn the creation of bacteria that are resistant to all antibiotics—creating invincible superbugs that could cause untreatable infections.

The CDC’s dive into drug dosing couldn’t explain why doctors are using the more powerful drugs. The study was done using a proprietary database of prescriptions recorded during patient discharges from a nationally representative sampling of more than 300 hospitals around the country. While it’s the largest study of its type to date, it doesn’t include other health data. It could be that physicians are truly encountering more drug-resistant infections or are simply assuming that infections are resistant and treating them accordingly.

Regardless, the CDC authors noted that “this trend is worrisome in light of the rising challenge of antibiotic resistance.”

On Wednesday, the UN General Assembly will address that challenge. It’s only fourth time in the UN’s history that a health topic has made the agenda. HIV, non-communicable diseases, and Ebola were the other topics that made the cut. The discussion will likely touch on policies that could spur doctors to cut back and be smart about antibiotic use. However, in many countries, people can currently get antibiotics without a prescription at all.

Experts are also likely to also focus on the agricultural sectors, which in many places (including the US) use vast amounts of antibiotics on livestock, commonly without clear medical need.